1. Field of the Invention
The invention relates generally to non-destructive inspection of a curved light reflective surface and more particularly, to a means for quantitatively evaluating the quality of the finish of a curved surface such as the body portion of a rolling mill roll; a coil convolution of metal strip; or an arc of strip length wrapped around a guide roll or a billy roll.
2. Description of the Prior Art
Rolling of metal in a rolling mill is an essential process for producing many steel products sold in strip or sheet form. Vitally important to the quality of the steel product is the surface appearance because it is an essential factor to the ornamental or esthetic appearance of items produced from the rolled product. The surface quality of stainless steel strip is usually given special attention. Surface imperfections on the roll body contacting the surface of the product during a rolling operation is transmitted to a surface of the rolled product. Thus, the surface quality of the finished product is inherently dependent upon the quality of the body surface of the rolling mill rolls, particularly the work rolls.
It is a common practice to change work rolls in a mill stand or final one or more mill stands of a tandem rolling mill on the basis of the tonnage of product rolled by the particular set of work rolls in the mill. This procedure is based on the assumption that the refurbished surface of newly replaced work rolls after each roll change will deteriorate to the same extent based on previous experience. Presently, the only method of evaluating the quality of the roll surface is by visual inspection thereof by trained personnel at either a roll finishing shop or at the mill site. Such a visual evaluation, however, does not constitute an objective and quantitative method of inspection, and, inherently allows variations in the finish of the work roll, which, in turn, allows variations in the quality of the finished product.
Because the quality of the roll surface is such an important factor to the appearance of the finished product, inspection of the roll body surface should be carried out before start up with a replacement roll or periodically after roll changing. Periodical evaluation of the work-roll surface and/or surface of the rolled product will provide an effective measure to ensure that the roll body surface meets a quality standard.
Disclosed in U.S. Pat. No. 3,549,264 is a goniophotometric instrument for providing quantitative values indicative of smoothness of metallic surfaces. The instrument determines values of specular reflectance, distinctness of image, and haze, of light reflected from a metallic surface, each of the values being indicative of the smoothness of the surface. A goniophotometer sold under the name DORIGON by Hunter Lab. of Fairfax, Va. operates in a manner similar to the instrument disclosed in the aforesaid U.S. Pat. No. 3,549,264 to provide appearance measurements based on angular resolution of a reflected image. A circular light spot is emitted from a light shaping orifice toward a specimen which can be held by clamps forming part of the instrument. However, the instrument can be adhered to a specimen surface by magnets. Because light must be reflected from a metallic surface by the instrument, it cannot be viewed at a proper position relative to a curved surface, such as the surface of a roll, the outer convolution of a coil of strip or an arc of strip length wrapped around a guide roll or a billy roll.
It is, therefore, an object of the present invention to provide a method and apparatus for quantitatively evaluating appearance characteristics of a curved metallic surface.
It is a further object of the present invention to provide a method and apparatus for measuring the values of specular reflectance, distinctness of image, and haze, of light reflected in a plane from a curved surface generally parallel to the longitudinal axis of the curved surface.
It is a still further object of the present invention to provide a mounting means allowing stable positioning of an apparatus for evaluating a curved reflective metallic surface.